Explosion-proof electrical indicator



y 1951 C. A. DE GIERS 2,554,978

EXPLOSION PROOF ELECTRICAL INDICATOR Filed Feb. 14, 1947 I 2Sheets-Sheet l IN VEN TOR. CLARENCE/4.05 5/5195 ATORZYE'Y May 29, 1951Filed Feb. 14, 1947 c. A. DE GIERS EXPLOSION PROOF ELECTRICAL INDICATOR2 Sheets-Sheet 2 INVENTOR.

CLARENCE/4.175 G/ER BMQW ATT RAEY Patented May 29, 1951 UNITED .;SPATENT OFFICE EXPLOSION PROOF ELECTRICAL INDICATOR Clarence Aide Giers,Forest Hills, N. Y a'ssignor to .The Liquidometer Corporation, LongIsland City, Y a corporation of Delaware Application February 14, 1947,Serial No. 728,409

'-ous liquid, such as gasoline in atank.

Indicators of thistype may be mounted closely adjacent to a tankcontaining *such liquids. 'As a result, there is a certain'latent dangerof an ignition of fuel fumes by electric sparks at the electriccomponentso'f the in'dicator. Such f-uel fumes are always present to acertain extent, as

leakage of vapors from "the tank is practically unavoidable,particularly when highly volatile fuel, such as gasoline, is containedin the tank. Furthermore, the presence of fuel fumes tends to corrodethe metal parts of the indicator, thereby increasing the "possibility"of failure.

According-1y, one *of the objects of the "invention is to provide meansfor greatly reducing or even eliminating the danger of explosion byignition of fuel fumes.

Another object of the invention to provide means b which electric partsof the indicator are protected against contact with corrosive fuelfumes.

Another object of the invention is to provide an explosion and corrosionproof indicator of the general type above referred to, which is ruggedand reliable in operation and relatively inexpensive to manufacture.

In the accompanying drawings, a preferred embodiment of the invention"is shown by way of illustration and not by way of limitation.

In the drawings:

Fig. 1 is a partial front View, half of which shows the internalcomponents of an indicator of the invention on line ll of Fig. 2;

Fig. 2 is a vertical sectional view of the indicator shown on Fig. 1;and

Fig. 3 is a typical wiring diagram showing schematically the electricalcomponents of the indicator.

The indicator is enclosed in a cylindrical housing 8 having its rear endenclosed by a head 9 screwed into housing 8 at H). The front of thehousing is closed by an integral annular head II which extends radiallyoutwardly to support a dial and other parts, and radially inwardly tosupport a rearwardly, andaxially, extending tubular indentation 12having its wall concentric with the outer housing 8 and integrallysealed at its rear end, thus forming an annular components of theinstrument.

indicated in Fig. 3.

bridge '23 (Fig/1). the jewel nut in place.

2 "hermetically "sealed chamber I 5 between the outer housing 8 andindentation l2. "The electrical equipment is an contained in-chamber 15.

Inside chamber l-5are mounted the electrical For example, there may beprovided three coils 1-6, two of which "are seen in Figs. 1 and 2 andall three These coils are wound on cores 16b of high permeabilitymagnetic material and have pole shoes 1 Eu "at both ends, shaped to litthe curvature of inner wall !2 as best seen "from Fig.1. Connections tothe coils, and other associated components are made through wiresbrought out through fittings hermetically sealed to the housing by pitchor other suitable packing T8.

The general construction of the indicating elements are described in a-co-pending application of Osterlund andGeiserfSer. No. 718,144, filedDecember 24, 1946, Electric MeasuringDev-ice with Torque Amplification,new Patent No.

2,486,972, "issued November 1, 1 949. Cooperating with the magneticfield produced by coils 16 through pole shoes [Ea-is a rotor made up ofa shaft I9 and two rotor sections Ilia of high cohousing ll. The rotorassembly is supported at the rear 'by a jewel bearing 23 mounted in theend of the cup "and locked in place by a locknut 2|. At the front end,the rotor assembly is supported by jewel bearing 22 mounted on a Alocknu-t 25. is used to keep The rotor assembly carries pointer 25movable over dial 26. The dial and rotor assembly are protected byconventional means such as a gasket 21, glass 28 and snap ring 29.

In operation, a transmitter such as shown schematically in Fig. 3 variesthe magnetic field of the indicator coils, and as is well known in theart the rotor follows this field to give an indication of thetransmitter position. Such an indicator may be operated with arelatively large air gap between the pole piece and the rotor, hence asubstantial wall of material having essentially unity permeability maybe introduced to provide the explosion proof feature.

The invention is illustrated and described with two spaced-apartmagnetic discs l9a and with coils l6 each having a shoe Ilia at each ofits ends. While this is the preferred form of the invention, it is alsopossible to use coils with radial axes and with an outer magnetic returnpath. In that case only a single disc would be used and the coils wouldhave shoes only on their inner ends.

As set forth more in detail in the said copending application ofOsterlund et al., Ser. No. 718,144, the magnetic discs l9a, shown inFig. 2, are both permanent magnets and are so arranged as to haveopposite polarity, i. e. the north pole of one is in the same radialdirection from the axis of the rotor shaft I9 as the south pole of theother, and vice versa. These permanent magnetic discs I9a are axiallyaligned with the several pole pieces I6a of the three electro-magnets ordeflecting coils 16 as shown. Then as the housing 8 and particularly thereentrant portion I2 thereof is of non-magnetic material, the fluxgenerated by the coils l6 and passing from the pole pieces lBa to andthrough the magnetic discs |9a will pass through the wall of thereentrant portion I2, so as to control the position of the rotor-inresponse to the resultant direction of magnetic flux of the three coilsl6. While three such coils are shown in the drawings, many telemeteringsystem circuits are known wherein but two deflecting coils are employed.The principles of this invention may be equally well applied to suchsystems, the important features being that the rotatable elements aresealed away from the electrical means by which the position of the rotoris controlled. Furthermore, it is necessary that the reentrant portion12 of the housing be of non-magnetic material, for the reason that ifthis were of magnetic material, the flux would by-pass the rotor magnetsand would have a clear path around these magnets through the housingportion. This would obviously defeat the intended purpose of the device,at least to a substantial and undesired extent.

In the invention all the electrical components are mounted in a sealedchamber. Should a spark arise from an cause within said chamber noexplosion would result since any inflammable fumes are excluded from thechamber. Since none of the electrical parts are exposed to dangerousfumes, this further protects these components from corrosion. Ifnecessary, the chamber could either be evacuated or filled with an inertgas.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described but may be used in otherways without departure from its spirit as defined by the followingclaim.

What is claimed is:

An electrical measurin instrument of the ratiometer type, comprising asubstantially cylindrical housing of non-magnetic material having itsfront end closed by an integral annular head, an imperforate reentrant,substantially cylindrical, cup shaped portion integral with said headand located substantially concentric with said cylindrical housing, arotor assembly mounted concentrically of and within said cup shapedportion and arranged for free rotation in respect thereto, said rotorassembly including an arbor and two magnetic members mounted thereon inaxially spaced relation, at least one of said members being permanentlymagnetized in a direction transverse of the axis of said arbor, aplurality of stationary deflecting coils each mounted on said annularhead and all disposed in the annular space between said cylindricalhousing and said cup shaped portion and at substantially uniformdistances from said rotor assembly with the axes of said coilssubstantially parallel with the axis of said arbor, a magnetic core foreach of said coils, pole pieces of magnetic material in contact witheach end of each said core and extending therefrom substantiallyradially inwardly toward the axis of said arbor, said members beinglocated on said arbor in substantially radial alignment with said polepieces, whereby to form magnetic circuits closed substantially throughsaid magnetic members, said pole pieces and said cores; and means forpreventing passage into contact with said coils of combustible andcorrosive gases to prevent corrosion of said coils and explosion of saidgases, including a cap member threaded to said cylindrical housing, anaperture in said cylindrical housing for the through passage ofelectrical leads for said coils. and hermetic sealing material in saidaperture about said electrical leads, so that said coils are enclosed ina sealed housing during normal operation of the instrument, while accessto theinterior of the instrument may be obtained by unscrewing said capmember from said cylindrical housing.

CLARENCE. A. DE GIERS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 383,444 Crompton et a1 May 29,1888 604,687 Moore May 24, 1898 1,248,246 Beede Nov. 27, 1917 2,003,163Warren May 28, 1935 2,320,946 Madden June 1, 1943 2,372,002 Kelley Mar.20, 1945

